The Collaborative International Dictionary of English v.0.48:

Reactionary \Re*ac"tion*a*ry\ (-[asl]*r[y^]), a.
   Being, causing, or favoring reaction; as, reactionary
   movements.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Reactionary \Re*ac"tion*a*ry\, n.; pl. Reactionaries
   (-r[i^]z).
   One who favors reaction, or seeks to undo political progress
   or revolution.
   [1913 Webster]

WordNet (r) 3.0 (2006):

reactionary
    adj 1: extremely conservative [syn: reactionary,
           reactionist, far-right]
    n 1: an extreme conservative; an opponent of progress or
         liberalism [syn: reactionary, ultraconservative,
         extreme right-winger]